A double sliding-plug door system used currently, which is generally a motor-driven screw stem, drives a nut assembly disposed on the screw stem to reciprocate, thereby driving a door leaf connected with the nut assembly. Generally speaking, the double sliding-plug door system is mostly applied to the field of public transportation vehicle doors like rail transit, and buses, and also has locking and unlocking functions. The double sliding-plug door system, which is generally applied to the above-mentioned fields, locks the nut assembly by an electromagnetic lock, thereby realizing the function of locking the door. For this type of double sliding-plug door system, the electromagnetic lock must be energized at any time to ensure the door locking stability. If the electromagnetic lock is de-energized, there is a risk when the door is automatically unlocked. However, most of the structures of locking the door by a mechanical lock in the prior art have the problem of complicated structures. As a system mainly composed of mechanical structures, complicated structures will bring problems such as poor reliability, big dead weight, and difficulty in control, and will threaten the personal safe of passengers especially when being applied to public transportation.